1. Field of the Invention
The invention relates to a touch system and method, and more particularly to a touch system and recognition method for an optical inputting type touch panel.
2. Description of the Related Art
With technological development, increased human machine interface functions in electronic products are being demanded. The display monitor with human machine interface not only displays information, but also provides a touch function. Thus, a user can interact with the display monitor and utilize fingers or a pen such as a dummy pen, static pen or an optical pen, to control the display monitor configured to receive at least one input type selected from the group consisting of capacitive, resistive, infrared, electromagnetic, optical, and surface acoustic wave touch screen. The touch screen may be employed as an input device with many types of apparatus, but any type of touch panel is sensitive to and degraded by moisture, heat, ultra-violet radiation and so on, especially optical inputting type touch panel. Because the radiation is impinged directly to the surface of the touch panel, the degradation is more influenced on the input signal.
A problem which is common to the optical inputting type touch panel, and not addressed by the prior art, is monitor aging caused by limited lifetime of the monitor. Monitor aging makes the photo-sensor generate unexpected sensing signals weaker than the normal ones, and appear as invalid touch signal to the system. Specially speaking, a plurality of photo-sensors configured inside the monitor, and converted the ambient light to electrical signal as background current. The background current may be declined as time pass by in view of the gradual decay of photo-sensors. Referring to FIG. 8 is a characteristic diagram of a photo-sensor, illustrating the relationship between the light response of the photo-sensors sensed by the displaying monitor and the operation time of the monitor. The background light maintains an output voltage at a stable level such that the signal response is sensitive enough to determine whether an input optical signal is light or shadow. The curve 81 is constituted by a series of sensing signals measured in constant illumination condition of ambient light, with operation time of the display device is increased, the sensing signal generated from the photo-sensors array in the display device will decrease. When the touch panel aging happened, the sensing signal contained background information for position coordinate(s) may be incorrect such that the valid input signal is ignored.
Accordingly, the system will fail to determine the valid touch signal, and this problem is more serious with the aging of the display monitor. It is therefore desirable to have a recognition mechanism that is able to calibrate the aging occurred in the optical inputting type touch panel during the normal operation.